RCE in Microsoft .NET runtime impacts widely deployed enterprise applications and services, enabling full system compromise if exploited.
CVE-2026-83520
Remote code execution via .NET deserialization of untrusted data.
Is CVE-2026-83520 being exploited?
Not confirmed. CVE-2026-83520 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 1.3% probability of exploitation in the next 30 days.
How severe is CVE-2026-83520?
CVE-2026-83520 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-83520?
Yes. A fix has been recorded for CVE-2026-83520. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-83520 affect?
CVE-2026-83520 affects Microsoft .NET runtime, .NET Framework, .NET Core applications, ASP.NET services. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-83520?
Install Microsoft update immediately; isolate exposed .NET services until patched.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated network attackers can execute arbitrary code on vulnerable .NET hosts, enabling full system compromise and lateral movement.
Immediate action required
- affected>= 3.5.0 and < 2.0.50727.9188 AND 3.0.30729.9171
- affected>= 3.0.0.0 and < 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0
- affected>= 4.7.0 and < 2.0.50727.9073 AND 3.0.30729.9070 AND 4.7.4150.0
- affected>= 4.8.0 and < 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0
- affected>= 4.8.1 and < 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0
- affected>= 4.7.0 and < 4.7.4150.0
- affected>= 4.8.0 and < 4.8.4811.0
- affected>= 4.8.0.0 and < 4.8.9363.0
- affected>= 17.14.0 and < 17.14.42
- affected>= 18.10.0 and < 18.10.4
- affected>= 10.0.0 and < 10.0.13
- affected>= 11.0.0 and < 11.0.0-rc.2
- affected>= 8.0.0 and < 8.0.32
- affected>= 9.0.0 and < 9.0.21
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.